It is advisable as well to use strict; together with tachyon's comment about the use of values in the innner loop this leads to: 
my (%authors, %subjects);
# and populate these hashes somehow

# the sort is irrelevant, at least for the part of the code you show
for my $from (keys %authors) {
   $authors{$from}->{$buddy}++
      for my $buddy map { split /\t/ } values %subjects;
}

[download]
and this seems rather strange because the values of %subjects never change, so each author ends up with exactly the same set of buddies. Is that what you intended? Or is some code missing/wrong in your post?

-- Hofmator

In reply to Re: Adding values to a hash of hashes by Hofmator
in thread Adding values to a hash of hashes by suzka99

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